Isopropanol is a very useful intermediate in organic synthesis as well as a commercially important solvent.
A process for the hydrogenation of acetone to isopropanol is described in EP-A-0379323. The hydrogenation of acetone to isopropanol is an exothermic process. As indicated in EP-A-0379323 too high reaction temperatures will induce excess hydrogenation decomposition of acetone, resulting in reduced yields of isopropanol. This problem is especially present when hydrogenating acetone. When compared with other ketones, acetone has a relatively low boiling point, and therefore, is easily gasified. Excess gasification can lead to hot spots and hydrogenation decomposition of acetone. Especially in the hydrogenation of acetone it is therefore necessary to precisely control the reaction temperature. One often used method to control the reaction temperature is the recycle of reaction product, e.g. isopropanol. Example 7 of EP-A-0379323 describes preheating of the reactant to 77° C. before entering a vertical reactor column having an inner diameter of 38.4 m, whereafter a reaction mixture at 113° C. was obtained from the outlet of the reactor. The reaction solution was divided into two portions. The first portion was taken out of the reaction system as a product. A second portion was fed back into the reactor by means of a recycle pump and combined with acetone to form a feed mixture for reaction. In the line for recycling the second portion a heat exchanger was provided. The reactor interior temperature was maintained at a predetermined temperature by controlling the jacket temperature of the heat exchanger. However, by recycling reaction product, that contains large amounts of isopropanol, the process becomes less economical and the amount of, for example, di-isopropyl ether, a major by-product, can increase. Furthermore the controllability of the temperature in the reactor itself is limited.